1. Add ENC28J60 Ethernet controller driver 
2. Add lwIP support (Please read "Readme.txt")
3. Add simple Http server demo application
4. Modify USART device write function to avoid sleep in ISR
5. Fix a bug in USART driver when using compiler optimization
6. Modify to make use the start-up code in libraries
7. Change the default build option for squeezing the executable file size
8. Modify source code alignment

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1622 bbd45198-f89e-11dd-88c7-29a3b14d5316